The IExpressionCategory interface contains properties and methods that are used to work with substitution category.
| Property name | Brief description | |
| Count | The Count property returns the number of substitutions in this category. | |
| Name | The Name property determines the name of the substitution category. | |
| Substitution | The Substitution property returns the parameters of the substitution with the specified index. | |
| SubstitutionByReduction | The SubstitutionByReduction property returns parameters of substitution with the specified abbreviated notation. |
| Method name | Brief description | |
| Add | The Add method adds a new substitution. | |
| Remove | The Remove method removes the specified substitution. |
See also: